The present invention relates to a method for end point detection of etching in a manufacturing process where etching is performed on an object to be processed using plasma.
Conventionally, an etching process using plasma has been widely applied to a semiconductor manufacturing process or a LCD substrate manufacturing process.
An etching apparatus therefor is provided in a processing chamber with, for example, an upper electrode and a lower electrode arranged in parallel to each other, in which, while etching gas is being introduced in the chamber, a high frequency voltage is applied between the upper electrode and the lower electrode in a state where an object to be processed (for example, a semiconductor wafer) is placed on the lower electrode to generate plasma in an etching gas atmosphere, thereby performing etching on a surface of the semiconductor wafer.
As a method for end point detection of etching for judging the end of an etching process, there are equipment analysis approaches such as mass spectrometry, emission spectral analysis, and the like, and since emission spectral analysis of plasma is relatively simple and the most sensitive of them, it has been widely employed.
A plasma emission measuring method based on this emission spectral analysis is a method where, from activated species such as radicals, ions or the like such as a decomposition product of an etching gas or a reaction product with the etching gas, attention is paid to a specific species which can be observed most easily and only the emission intensity of the selected species is measured. For example, in a case that a silicon oxide film has been etched using CF group etching gas such as CF4 or the like, a specific wavelength (483.5 nm or the like) of CO* which is a reaction product with the etching gas is detected. Also, when a silicon nitride film is etched using CF group etching gas such as CF4 or the like, a specific wavelength (674 nm or the like) of N* which is a reaction product with the etching gas is detected and an end point is detected on the basis of change points of respective detection intensities. Thus, in the conventional method for end point detection of etching, a wavelength used for the end point detection of etching is changed according to the etching process used.
In a case of the conventional method for end point detection of etching, however, since the end point detection is performed while monitoring only a specific wavelength in emission spectra emitted from plasma, a specific wavelength must have been found for each process.
Furthermore, in an etching process for a low opening etching, i.e., an etching process where the area of a mask pattern occupying a semiconductor wafer is large and an area to be etched is small, since occurrence of the activated species used for an end point detection of etching is reduced and change in emission intensity of a specific wavelength becomes small, there is a problem that the S/N ratio deteriorates so that an exact end point detection of etching becomes difficult.
Also, in U.S. Pat. No. 5,288,367, there has been proposed a method where a specific wavelength of an emission spectrum is automatically determined using an approach of a principal component analysis and an end point of etching is detected on the basis of the specific wavelength.
According to this method, a specific wavelength can automatically be determined, but the method is similar to the conventional method for end point detection of etching regarding the point that the end point of etching is detected using only the specific wavelength.
An object of the present invention is to provide a method for end point detection of etching where an end point of etching can securely be detected, despite the presence of noise, even in a low opening etching process.
The present invention provides a method for end point detection of etching where, when etching is performed on an object to be processed using plasma, emission spectra are sequentially detected by detecting means and an end point of etching is detected on the basis of change in the emission spectra, comprising: the step of etching a sample in advance prior to etching of the object and sequentially measuring full-spectra of plasma during the etching of the sample; and the step of obtaining weighting factors for each wavelength, where the weighting factors have weighted all wavelengths of each of the full-spectra accumulated until end of etching of the sample according to respective emission intensities of the full-spectra, and further comprising: the step of adding the emission intensities of all the wavelengths for each of full-spectra sequentially measured during etching of the object in addition of the weighting factors; and the step of detecting an end point of the etching on the basis of the degree of change of addition value of the emission intensities for each of the full-spectra sequentially measured. Also, the present invention detects the end point of etching using a differential value of the addition value in the above method for end point detection of etching.
Furthermore, the present invention provides a method for end point detection of etching where, when etching is performed on an object to be processed using plasma, emission spectra are sequentially detected by light detecting means and an end point of etching is detected on the basis of change in the emission spectra, comprising: the step of, prior to etching of the object, etching an object to be processed of the same kind of the object to sequentially measure full-spectra of plasma generated during the etching step; and the step of performing a principal component analysis on all wavelengths of each of full-spectra accumulated until end of etching using respective emission intensities of all the wavelengths; and further comprising the step of obtaining a principal component score on the basis of the respective emission intensities of all the wavelengths and the principal component obtained in the principal component analysis; and the step of detecting an end point of etching on the basis of the substantial change in the principal component score for each of the full-spectral sequentially measured.
Also, in the method for end point detection of etching of the present invention, as the above principal component score, a first principal component score is employed. Furthermore, using the differential value of the principal component score, the end point of etching is detected.